Magnetic Coupling between Grains in Post-annealed CoPt-based Alloy Thin Film Improved by Cr Addition

Segregation of Cr at the grain boundaries of post annealed CoPt and CoCrPt alloy/Cr thin film systems has been investigated for decreasing magnetic coupling between grains in magnetic thin film. It has been found that Cr is diffused from the Cr underlayer into the CoPt magnetic layer during this post annealing, resulting segregation at the grain boundaries. In addition to the Cr diffusion from underlayer, Cr is diffused from magnetic grains in CoCrPt/Cr structure case. Therefore, the addition of Cr to as-deposited Co-based magnetic film causes increase of the segregation. In the case of 20 nm-thick CoCrPt/50 nm-thick Cr system, the coercivity of maximum value 4.6 kOe and Hc/Hkgrain of maximum value 0.46 were obtained after post annealing at 460°C.